A passive optical network (PON) technology is one of the most widely applied Fiber To The Home (FTTH) technologies. Mainstream PON standards include gigabit passive optical network (GPON) developed and submitted by the Full Service Access Network (FSAN) organization and formulated by the International Telecommunication Union standardization organization (ITU-T), and Ethernet passive optical network (EPON) formulated by the Institute of Electrical and Electronics Engineers (IEEE) of the United States.
A network architecture of a conventional PON system mainly includes such parts as an optical network unit (ONU), an optical distribution network (ODN), and an optical line terminal (OLT). As shown in FIG. 1-a, a downstream direction is from the OLT to the ONUs through the ODN, where data is transferred in a broadcast manner. A user equipment such as a portable computer or telephone sends upstream data to the OLT through an ONU and the ODN. The upstream data is sent in a manner of using the time division multiple access (TDMA, Time Division Multiple Access) technology. The ODN network uses a passive optical splitter to combine optical signals of the ONUs. Therefore, the ONUs need to stop sending optical signals in unauthorized periods, that is, stop sending data. The upstream data sent by the ONUs is burst data, and only one ONU is allowed to send upstream data at a time. The conventional PON system mainly satisfies access requirements of the last kilometer, where a small number of ONUs are connected to the OLT through the ODN, and a coverage radius is no more than 20 km, resulting in that many OLTs need to be deployed in the system for the conventional network architecture, which increases equipment investment and maintenance costs in one aspect, and increases management and maintenance complexity of the entire system in another aspect.
A long-reach passive optical network (LR-PON) is proposed based on the conventional PON system, and is mainly used to expand the coverage area of a PON system. In the optical transport network (OTN) standard G.709, the LR-GPON based on the GPON system of the OTN has been adopted, and has been partially put into commercial use.
A network architecture of an existing LR-GPON system may be shown in FIG. 1-b. A terminal processing device 12 and a central office processing device 13 are connected between an optical distribution network 11 and an optical line terminal 14 that is deployed in a central equipment room. An optical network unit 10 sends data over the optical distribution network 11. The terminal processing device 12, after converting an upstream burst data stream combined by the optical distribution network 11 into a contiguous data stream, maps the contiguous data stream into an optical transport network protocol frame, and transports the contiguous data stream over a long distance in a manner of combining the optical transport network and wavelength division multiplexing (WDM) technologies. The central office processing device 13 demaps the contiguous data stream in the optical transport network, to recover the contiguous data stream and sends the contiguous data stream to the optical line terminal 14 for processing.
In an existing technical solution, the central office processing device 13 defines, in a manner of determining a data gap in a data stream, a start time point and an end time point for sending data by the central office processing device 13 to the optical line terminal 14. For example, when the central office processing device 13 detects a physical layer overhead upstream (PLOu) in a process of demapping upstream data, the central office processing device 13 starts to send the received upstream data to the optical line terminal 14; and after detecting tens of consecutive bytes of 0s, the central office processing device 13 determines that an upstream burst ends, and stops sending data to the optical line terminal 14.
However, in an actual application, a too long data gap reduces an effective bandwidth. Therefore, a data gap between signals sent to the OLT by adjacent ONUs usually has several bytes only. As a result, a data sending boundary of a single ONU cannot be determined by using the above manner of determining a data gap, resulting in that each central office processing device can only be connected to the OLT through an independent PON access port 15, which reduces bearing efficiency of the PON access port in one aspect, and limits networking manners of a long-reach passive optical network in another aspect.